This code succeeds on desktop fsi, but fails on coreclr fsi

[KevinRansom]

[<Struct>]
type ToStringStruct =
  struct
    val x : int
    new(x) = {x=x}
    override this.ToString() = string this.x
  end
let a = new ToStringStruct(123)

With this stackframe:

C:\Users\kevinr\AppData\Local\Temp\3vqfda12.xew>dotnet fsi

Microsoft (R) F# Interactive version 10.4.0 for F# 4.6
Copyright (c) Microsoft Corporation. All Rights Reserved.

For help type #help;;

> [<Struct>]
- type ToStringStruct =
-   struct
-     val x : int
-     new(x) = {x=x}
-     override this.ToString() = string this.x
-   end
- let a = new ToStringStruct(123)
- ;;

Assertion Failed
Unknown exception seen in compiler: System.TypeLoadException: Could not load type 'FSI_0002' from assembly 'FSI-ASSEMBLY, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
   at System.Reflection.Emit.TypeBuilder.TermCreateClass(RuntimeModule module, Int32 tk, ObjectHandleOnStack type)
   at System.Reflection.Emit.TypeBuilder.CreateTypeNoLock()
   at System.Reflection.Emit.TypeBuilder.CreateTypeInfo()
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.TypeBuilder.CreateTypeAndLog(TypeBuilder ) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 144
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.traverseTypeRef@1998.Invoke(ILTypeRef tref) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2038
   at Microsoft.FSharp.Primitives.Basics.List.iter[T](FSharpFunc`2 f, FSharpList`1 x) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\local.fs:line 91
   at Microsoft.FSharp.Collections.ListModule.Iterate[T](FSharpFunc`2 action, FSharpList`1 list) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\list.fs:line 111
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.traverseType@1993.Invoke(CollectTypes allTypes, ILType ty) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 1993
   at Microsoft.FSharp.Primitives.Basics.List.iter[T](FSharpFunc`2 f, FSharpList`1 x) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\local.fs:line 91
   at Microsoft.FSharp.Collections.ListModule.Iterate[T](FSharpFunc`2 action, FSharpList`1 list) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\list.fs:line 111
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.traverseTypeDef@1962.Invoke(ILTypeRef tref, ILTypeDef tdef) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 1988
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.traverseTypeRef@1998.Invoke(ILTypeRef tref) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2007
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.createTypeRef(Dictionary`2 visited, Dictionary`2 created, emEnv emEnv, ILTypeRef tref) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2040
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.buildTypeDefPass4(Dictionary`2 visited, Dictionary`2 created, FSharpList`1 nesting, emEnv emEnv, ILTypeDef tdef) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2045
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.buildModuleFragment@2083-1.Invoke(ILTypeDef tdef) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2083
   at Microsoft.FSharp.Primitives.Basics.List.iter[T](FSharpFunc`2 f, FSharpList`1 x) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\local.fs:line 91
   at Microsoft.FSharp.Collections.ListModule.Iterate[T](FSharpFunc`2 action, FSharpList`1 list) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\list.fs:line 111
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.buildModuleFragment(cenv cenv, emEnv emEnv, AssemblyBuilder asmB, ModuleBuilder modB, ILModuleDef m) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2083
   at FSharp.Compiler.AbstractIL.ILRuntimeWriter.emitModuleFragment(ILGlobals ilg, emEnv emEnv, AssemblyBuilder asmB, ModuleBuilder modB, ILModuleDef modul, Boolean debugInfo, FSharpFunc`2 resolveAssemblyRef, FSharpFunc`2 tryFindSysILTypeRef) in C:\kevinransom\visualfsharp\src\absil\ilreflect.fs:line 2146
   at FSharp.Compiler.Interactive.Shell.FsiDynamicCompiler.ProcessInputs(CompilationThreadToken ctok, ErrorLogger errorLogger, FsiDynamicCompilerState istate, FSharpList`1 inputs, Boolean showTypes, Boolean isIncrementalFragment, Boolean isInteractiveItExpr, FSharpList`1 prefixPath) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1051
   at FSharp.Compiler.Interactive.Shell.FsiDynamicCompiler.EvalParsedDefinitions(CompilationThreadToken ctok, ErrorLogger errorLogger, FsiDynamicCompilerState istate, Boolean showTypes, Boolean isInteractiveItExpr, FSharpList`1 defs) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1139
   at FSharp.Compiler.Interactive.Shell.clo@1871-474.Invoke(FsiDynamicCompilerState istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1878
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.InteractiveCatch[b](ErrorLogger errorLogger, FSharpFunc`2 f, b istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1825

   at FSharp.Compiler.CompileOps.OutputExceptionR@607.Invoke(StringBuilder os, Exception error) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1581
   at FSharp.Compiler.CompileOps.OutputPhasedErrorR(StringBuilder os, PhasedDiagnostic err, Boolean suggestNames) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1584
   at FSharp.Compiler.CompileOps.OutputPhasedDiagnostic(StringBuilder os, PhasedDiagnostic err, Boolean flattenErrors, Boolean suggestNames) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1591
   at FSharp.Compiler.CompileOps.report@1696-1.Invoke(PhasedDiagnostic err) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1714
   at FSharp.Compiler.CompileOps.CollectDiagnostic(String implicitIncludeDir, Boolean showFullPaths, Boolean flattenErrors, ErrorStyle errorStyle, Boolean warning, PhasedDiagnostic err, Boolean suggestNames) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1750
   at FSharp.Compiler.CompileOps.OutputDiagnostic(String implicitIncludeDir, Boolean showFullPaths, Boolean flattenErrors, ErrorStyle errorStyle, Boolean isError, StringBuilder os, PhasedDiagnostic err) in C:\kevinransom\visualfsharp\src\fsharp\CompileOps.fs:line 1759
   at FSharp.Compiler.Interactive.Shell.PrintError@510-4.Invoke(StringBuilder arg10@, PhasedDiagnostic arg20@) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 510
   at FSharp.Compiler.Lib.writeViaBufferWithEnvironmentNewLines[a](TextWriter os, FSharpFunc`2 f, a x) in C:\kevinransom\visualfsharp\src\fsharp\lib.fs:line 333
   at FSharp.Compiler.Interactive.Shell.PrintError@507-1.Invoke(Unit unitVar0) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 510
   at FSharp.Compiler.CompileOptions.DoWithColor[a](ConsoleColor newColor, FSharpFunc`2 f) in C:\kevinransom\visualfsharp\src\fsharp\CompileOptions.fs:line 1835
   at FSharp.Compiler.Interactive.Shell.Utilities.ignoreAllErrors(FSharpFunc`2 f) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 87
   at FSharp.Compiler.Interactive.Shell.FsiStdinSyphon.PrintError(TcConfigBuilder tcConfig, PhasedDiagnostic err) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 505
   at FSharp.Compiler.Interactive.Shell.ErrorLoggerThatStopsOnFirstError.DiagnosticSink(PhasedDiagnostic err, Boolean isError) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 546
   at FSharp.Compiler.ErrorLogger.ErrorLoggerExtensions.ErrorLogger.ErrorRecovery(ErrorLogger x, Exception exn, range m) in C:\kevinransom\visualfsharp\src\fsharp\ErrorLogger.fs:line 417
   at FSharp.Compiler.ErrorLogger.ErrorLoggerExtensions.ErrorLogger.StopProcessingRecovery(ErrorLogger x, Exception exn, range m) in C:\kevinransom\visualfsharp\src\fsharp\ErrorLogger.fs:line 431
   at FSharp.Compiler.ErrorLogger.stopProcessingRecovery(Exception exn, range m) in C:\kevinransom\visualfsharp\src\fsharp\ErrorLogger.fs:line 486
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.InteractiveCatch[b](ErrorLogger errorLogger, FSharpFunc`2 f, b istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1825
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.ExecInteraction(CompilationThreadToken ctok, TcConfig tcConfig, FsiDynamicCompilerState istate, ParsedFsiInteraction action, ErrorLogger errorLogger) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 1871
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.execParsedInteractions(CompilationThreadToken ctok, TcConfig tcConfig, FsiDynamicCompilerState istate, FSharpOption`1 action, ErrorLogger errorLogger, FSharpOption`1 lastResult) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2018
   at FSharp.Compiler.Interactive.Shell.clo@2050-477.Invoke(CompilationThreadToken ctok, TcConfig tcConfig, FsiDynamicCompilerState istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2051
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.mainThreadProcessAction[a,b](a ctok, FSharpFunc`2 action, b istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2031
   at FSharp.Compiler.Interactive.Shell.FsiInteractionProcessor.mainThreadProcessParsedInteractions(CompilationThreadToken ctok, ErrorLogger errorLogger, FSharpOption`1 action, FsiDynamicCompilerState istate) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2050
   at FSharp.Compiler.Interactive.Shell.res@2113-58.Invoke(CompilationThreadToken ctok, ErrorLogger errorLogger, Tuple`2 tupledArg) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2113
   at <StartupCode$FSharp-Compiler-Interactive-Settings>.$Fsiaux.FSharp-Compiler-Interactive-IEventLoop-Invoke@50-1.Invoke(Unit x) in C:\kevinransom\visualfsharp\src\fsharp\fsiaux.fs:line 50
   at <StartupCode$FSharp-Compiler-Interactive-Settings>.$Fsiaux.run@41-4.Invoke(FSharpFunc`2 f) in C:\kevinransom\visualfsharp\src\fsharp\fsiaux.fs:line 41
   at Microsoft.FSharp.Primitives.Basics.List.iter[T](FSharpFunc`2 f, FSharpList`1 x) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\local.fs:line 91
   at Microsoft.FSharp.Collections.ListModule.Iterate[T](FSharpFunc`2 action, FSharpList`1 list) in C:\kevinransom\visualfsharp\src\fsharp\FSharp.Core\list.fs:line 111
   at <StartupCode$FSharp-Compiler-Interactive-Settings>.$Fsiaux.run@39.Invoke(Unit unitVar0) in C:\kevinransom\visualfsharp\src\fsharp\fsiaux.fs:line 41
   at FSharp.Compiler.Interactive.SimpleEventLoop.FSharp-Compiler-Interactive-IEventLoop-Run() in C:\kevinransom\visualfsharp\src\fsharp\fsiaux.fs:line 48
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at FSharp.Compiler.Interactive.Shell.Utilities.callInstanceMethod0[a](Object obj, Type[] typeArgs, String nm) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 116
   at Sample.FSharp.Compiler.Interactive.Main.evaluateSession@235-4.EventLoopRun() in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsimain.fs:line 253
   at FSharp.Compiler.Interactive.Shell.runLoop@2356.Invoke(Unit unitVar0) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2361
   at FSharp.Compiler.Interactive.Shell.DriveFsiEventLoop(FsiEvaluationSessionHostConfig fsi, FsiConsoleOutput fsiConsoleOutput) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2379
   at FSharp.Compiler.Interactive.Shell.FsiEvaluationSession.Run() in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsi.fs:line 2794
   at Sample.FSharp.Compiler.Interactive.Main.evaluateSession(String[] argv) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsimain.fs:line 305
   at Sample.FSharp.Compiler.Interactive.Main.MainMain(String[] argv) in C:\kevinransom\visualfsharp\src\fsharp\fsi\fsimain.fs:line 339

C:\Users\kevinr\AppData\Local\Temp\3vqfda12.xew>#quit;;

[dsyme]

I'm just guessing but I'd imagine it's this #if'd code here https://github.com/Microsoft/visualfsharp/blob/master/src/absil/ilreflect.fs#L2006

[KevinRansom]

Wedding Anniversary today, I will look at it tomorrow.